Meteorology Reviewer PDF

LEC 1 Atmosphere - protects us; life-giving blanket of air that surrounds the Earth Composition: Nitrogen, Oxygen, Water Vapor, Carbon Dioxide, Ozone ○ Water Vapor is the most abundant variable gas; essential in the earth’s heat-energy balance ○ Oceans are huge reservoir...

LEC 1 Atmosphere - protects us; life-giving blanket of air that surrounds the Earth Composition: Nitrogen, Oxygen, Water Vapor, Carbon Dioxide, Ozone ○ Water Vapor is the most abundant variable gas; essential in the earth’s heat-energy balance ○ Oceans are huge reservoir of CO2, Greenhouse gas (increasing concentration = increasing average surface temperature) Vertical Structure of the Atmosphere - the atmosphere is composed of layers Air Density ○ Mass of air in a given volume, greatest at the Earth’s surface, decreases as we go up the atmosphere ○ Gravity pulls down the air above, which compresses air molecules together. More air above = greater squeezing effect Air Pressure ○ Push force divided by the are P = F/A; total mass of air above any point ○ Atmospheric pressure decreases with increasing height Layers of the Atmosphere - defined by temperature ○ Troposhere - contains all weather we are familiar with; air temperature decreases with height (lapse rate) ○ Stratosphere - temperature increases with height (temperature inversion); lapse rate is zero; ozone heating the layer using uv energy ○ Mesosphere - temperature decreases with height; lowest temperature is reached at the top of this layer ○ Thermosphere - air molecules will move very far before colliding with another molecule Mesopause - boundary separating mesosphere and thermosphere ○ Exosphere - upper limit of the atmosphere ○ Ionosphere - not considered a layer; electrified region within the upper atmosphere Weather vs. Climate ○ Weather - condition of the atmosphere at any particular time and place; always changing ○ Climate - average weather; accumulations of daily and seasonal weather events Meteorology - study of the atmosphere and its phenomena LEC 2 Temperature ○ Heat Energy - kinetic energy due to the motion of atoms and molecules; atoms and molecules are not moving at the same speed ○ Temperature - average speed of atoms and molecules Cooling Air -> slower movement of molecules -> crowded -> air becomes more dense Warm Air -> faster movement of molecules -> farther apart -> air becomes less dense Heat - energy transferred from one object to another because of temperature difference (ex. Hot Mug placed in cool lake - drastic decrease in temp sa mug) Specific Heat ○ Heat Capacity - amount of energy to be absorbed para uminit ○ Specific Heat - heat capacity of a substance per unit mass Water heats slowly and cools slowly; it can store large amount of energy while undergoing small temperature changes Latent Heat - heat energy required to change a substance from one state to another ○ Evaporation is a cooling process; more energetic molecules escape easily, which results in a decrease in motion of left behind molecules. Lower average speed = lower temperature ○ Sensible Heat - heat energy released when water vapor condenses to liquid ○ Cooling process: heat energy taken from the environment (ex. evaporation, melting)  ○ Heating process: heat energy released to the environment (ex. Condensation, freezing) Heat Transfer in the Atmosphere: ○ Conduction - transfer of heat from molecule to molecule; heat transfer is from warmer to colder region; greater temp difference = more rapid heat transfer ○ Convection - transfer of heat by mass movement of a fluid Air molecules gain energy by conduction from the hot surface, cooler heavier air sinks (more dense), heated air expands (less dense) Rising air always cools by expansion, sinking air warms by compression ○ Radiation - transfer of energy without the space between two objects being heated All things whose temperature is above absolute zero emit radiation Wavelength of radiation depends on temperature (higher temp = short wavelength) Increasing temp = more total radiation Absorption and Emission ○ All objects emit and absorb energy. ○ Day: absorption > emission (earth’s surface warms) ○ Night: emission > absorption (earth’s surface cools) ○ Blackbody - perfect absorber (absorbs all radiation); perfect emitter (emits max radiation) ○ Radiative Equilibrium Temperature - average temp where rate of absorption = rate of emission Atmospheric Greenhouse Effect ○ CO2 and H2O are strong absorbers of Infrared ○ Most IR energy from the Earth’s surface keep the lower atmosphere warm Scattered and Reflected Light LEC 3 Seasons - amount of solar energy received at the Earth’s surface determined by: 1. Angle at which sunlight strikes the Earth’s surface 2. Hours of daylight (longer daylight hours = more solar energy reaches the surface) Summer, Autumn, Winter, Spring Temperature Variations ○ Daytime warming As the sun rises, sunlight warms the ground, ground warms the air by conduction. As the sun rises higher, air in contact with the ground gets warmer Convection begins near the surface, and thermals help to distribute heat. ○ Nighttime Cooling As the sun lowers, energy spreads over a larger area, which reduces the heat that warms the ground. In the early evening, the Earth’s surface and air above begin to cool by radiating infrared energy. Hotter surface air transfers energy through conduction, which quickly radiates Temperature Variations - gets progressively smaller as we move higher ○ Factors: humidity, proximity to bodies of water, urbanization Air temperature data: mean daily temperature, normal temperature, monthly average temperature, annual range of temperature LEC 4 Hydrologic Cycle ○ Water infiltrates into the ground through percolation, which forms groundwater. Water underground moves slowly. ○ Plants give up moisture through transpiration Evaporation - escape of fast enough water molecules  Saturation - total number of molecules escaping must be balanced by the number of returning. Molecules escaping = molecules returning ○ Point of Saturation - amount of water vapor molecules ay hindi na kayang magcarry ng more molecules ○ Saturation is more likely to occur in cool than in warm air (mas malamig na hangin means mas konti ung max amt of water vapor molecules ang kaya niyang ihold at saturation kaysa sa warm air) Moisture Variables ○ Absolute Humidity - mass of water vapor in a given volume of air (insert eq.) Temperature affects humidity (mass), warm air = less dense; cool air = more dense ○ Vapor Pressure Actual Vapor Pressure - total air pressure x % of water vapor (by volume) Higher water vapor pressure = more water vapor molecules Saturation Vapor Pressure - actual vapor pressure at saturation At higher temperature, more vapor molecules are needed to saturate the air -> vapor pressure increases with temperature Fewer molecules escaping -> fewer vapor molecules to maintain saturation ○ Relative humidity - how close the air to being saturated. RH = (actual vp/saturation vp) x 100 Change in RH can be caused by changing the air’s water vapor content or changing the air temperature. ○ Dew-point Temperature - temperature to which air would have to be cooled for saturation to occur. Good indicator of the air’s actual water vapor content; high dew point = high water vapor content Continued cooling of the air below dew point condenses some of the vapor into tiny cloud droplets ○ “Maalinsangan” Air temperature is high; RH is low (mabilis matuyo tubig; sweat evaporates quickly) Air temperature is high; RH is high (sweat does not evaporate and collects on skin; less evaporation means less cooling) ○ Heat Index - combines air temperature with relative humidity Near-ground Condensation ○ Dew - twigs, leaves, and blades of grass cool below dew point, water vapor condenses and forms dew. (Freezing air temp = frozen dew) Lumalamig ung ground pag gabi/right before dawn because the Earth releases energy More likely to form on clear and calm nights. In clear nights - no clouds to absorb and return IR radiation; konting water vapor In calm nights - no turbulence to mix the air; coldest air will be at ground level. ○ Condensation Nuclei Hygroscopic - water seeking; RH lower than 100% Hydrophobic - water repelling; RH above 100% ○ Haze - layer of dust or salt particles Dry Haze - forms when RH is below the point where water vapor begins to condense. Wet haze - RH increases as the air cools at night, condensation may begin on hygroscopic nuclei. ○ Fog - formed by cooling (air is cooled below dew point) or evaporation and mixing Visibility lowers to 100%). ▪ The smaller the droplet, the higher the supersaturation needed ○ Solute Effect On hygroscopic condensation nuclei, condensation may begin even when RH is well below 100%. When condensation begins on a salt particle, they dissolve, forming a solution. Since salt ions bind closely with water molecules, it is more difficult for water molecules to evaporate Result of this effect: equilibrium vapor pressure is reduced. Equilibrium can be achieved even at RH ~78%. Thus, there are more, but smaller, cloud droplets over land and fewer, but larger, cloud droplets over the ocean. Collision-Coalescence Process ○ Coalescence - Merging of large cloud droplets with smaller drops as it moves along its path. The amount of time the droplet spends in the cloud is also an important factor Collision does not always guarantee coalescence – sometimes droplets bounce apart during collision. Larger drops fall faster than smaller drops The factors affecting the collision-coalescence process in warm clouds: 1. Cloud’s liquid water content – most important 2. Range of droplet sizes 3. Cloud thickness 4. Updrafts of the cloud 5. Electric charge of droplets and electric field in the cloud Thin, stratus clouds with slow updrafts → Drizzle Towering cumulus clouds with rapid rising air → Heavy rain showers Ice-Crystal (Bergeron) Process ○ During the ice-crystal (Bergeron) process, ice crystals grow larger at the expense of the surrounding water droplets. Accretion – the growth of falling ice crystals due to freezing of supercooled droplets on contact. The icy matter that forms is called graupel. Aggregation – chain reaction of collision and sticking of falling crystals with other crystals, forming snowflakes. Cloud Seeding - put into the cloud some particles that will enhance both condensation and cloud droplet growth. There should be presence of clouds initially as seeding does not generate clouds. ○ Aim: produce more rain and let the cloud rain earlier ○ Warm Cloud Seeding - Introduces salt into the cloud and through the solute effect, they facilitate the formation and growth of cloud droplets ○ Cold Cloud Seeding - Artificial freezing nuclei (such as AgI), which has similar crystalline structure to ice crystals, are introduced to boost the Bergeron process. Precipitation Types: ○ Rain - Falling drop of water with diameter ≥0.5 mm. If the drops are smaller, they are called drizzles. Virga - rain that never reaches the surface because of the low humidity causing rapid evaporation, and they appear to hang in the air.  If this updraft (a) weakens, (b) changes direction, or (c) becomes a downdraft, the suspended raindrops will fall to the ground suddenly as rain shower. If the shower is excessively heavy, it is called a cloudburst. Continuous rain usually falls from a layered cloud that covers a large area and has small vertical currents → nimbostratus clouds Rainfall Intensity - Amount of rain that falls in a given period; based on the accumulation during a certain interval of time. Very Light Rains - scattered drops, do not completely wet surface Light Rains - 2.5mm/hr Moderate - 2.5-7.5mm Heavy - greater than 7.5mm ○ Snow - White (or translucent) ice crystals in complex hexagonal shapes that often join together to form snowflakes Fallstreaks - When ice crystals and snowflakes fall from high cirrus clouds ○ Sleet - Tiny ice pellets formed when falling snowflakes fall into warmer air and melt, then fall through a deep subfreezing surface layer of air and turns back into ice ○ Freezing Rain/Glaze - Forms when the subfreezing surface layer is too shallow to freeze raindrops as they fall The raindrops reach the ground as supercooled liquid and upon a cold object, the drops spread out and almost immediately freeze. If the drops are small (